At its inception radio telephony was designed, and used for, voice communications. As the consumer electronics industry continued to mature, and the capabilities of processors increased, more devices became available for use that allowed the wireless transfer of data between devices. Also more applications became available that operated based on such transferred data. Of particular note are the Internet and local area networks (LANs). These two innovations allowed multiple users and multiple devices to communicate and exchange data between different devices and device types. With the advent of these devices and capabilities, users (both business and residential) found an increasing need to transmit data, as well as voice, from mobile locations.
The infrastructure and networks which support this voice and data transfer have likewise evolved. Limited data applications, such as text messaging, were introduced into the so-called “2G” systems, such as the Global System for Mobile (GSM) communications. Packet data over radio communication systems were implemented in GSM with the addition of the General Packet Radio Services (GPRS). 3G systems introduced by Universal Terrestrial Radio Access (UTRA) standards made applications like surfing the web more easily accessible to millions of users (and with more tolerable delay). Thus, numerous radio access technologies (RATs), such as e.g. Wideband Code Division Multiple Access (WCDMA), OFDMA, TDMA, TD-SCDMA, and others, can be found in use today in wireless systems such as e.g. GSM/GPRS/EDGE, UMTS, UMTS-LTE, WLAN, WiFi, etc.
Even as new network designs are rolled out by network manufacturers, future systems which provide greater data throughputs to end user devices are under discussion and development. For example, the so-called 3GPP Long Term Evolution (LTE) standardization project is intended to provide a technical basis for radio communications in the years to come. This evolution of network designs has resulted in various network operators deploying their networks in various frequency bands with different RATs in various geographical areas. As a result of this, a user equipment (UE) which supports several frequency bands and/or several different RATs will need to be able to, among other things, search for cells and service in a correct frequency band and/or RAT.
The rapid development of new standards for mobile telephony and other communication technologies and the even more rapid addition of new features to the existing standards drive higher design costs for devices which use the currently existing architectures. For example, devices which enable access to a particular RAT or RATs typically have a software (SW) architecture that is tailored to that RAT(s) and its current features. When a new RAT or feature is added to a multi-RAT UE device architecture, not only the new RAT/feature has to be implemented in the architecture but also the legacy implementations have to be adapted, which process typically seriously affects the software implementation and adds significantly to the devices' costs.
This methodology for introducing a new RAT, or a new functionality to an existing RAT, makes the SW architecture of UEs complex and it becomes difficult to make the modifications that are necessary to adapt to such changes. Additionally, development is often performed at different geographical sites, sometimes located in different continents, causing the integration to be even more complicated and costly.
In addition to software architecture modifications, hardware changes may also be necessary or advisable due to RAT adaptations in UEs. For example, in a multi-RAT UE, it is often desirable to share (as much as possible) the hardware (HW) in the system. One example of potentially shareable hardware in a multi-RAT device is a HW accelerator. However, each user (i.e., RAT) of a HW accelerator needs to keep its own context to avoid unwanted coupling, i.e., dependency, with other RAT's algorithms or modules. One way to enable each user to keep its own context is to include, and use, several register pages in the HW accelerator. However, the number of pages available in the register is fixed upon design of the silicon associated with the multi-RAT UE and cannot be changed later. This makes this decoupling strategy somewhat inflexible with respect to subsequent RAT or feature additions.
Moreover, regarding algorithms used in multi-RAT devices, these algorithms can be implemented in either software (SW) or hardware (HW) and typically have a stronger coupling with each user or RAT than is desirable. This coupling or dependency can cause unwanted redesign of neighboring blocks when one block is changed in a UE (or subcomponent of the UE). Also, as the number of RATs increases, unknown dependencies and side effects can arise from other parts of the system that may be undesirable. Still further, in a multi-RAT system the higher data rates and shorter transmission time intervals (TTIs) can cause ever higher interrupt loads in systems designed with a central controller.
Still further, when adding new functionality, e.g., additional RAT capabilities, to a UE the dependencies between the different activities, such as paging channel (PCH) reception and measurements can make it cumbersome to implement, since new combinations of use cases need to be considered and then hard coded. The Layer 1 RAT software typically uses the radio for different purposes, such as channel reception and measurements. As there is no common planning between RATs in conventional multi-RAT architectures, it is difficult to handle specific use cases where the active RAT cannot handout the necessary radio time. In an attempt to avoid radio usage conflicts, each use case, such as paging channel reception with serving cell measurements, is typically combined and/or synchronized. However, conflicts cannot always be resolved, and a fair handling between RATs/functionalities may be impossible.
Moreover, when adding additional RATs to a multi-RAT architecture (compared, e.g., to having only GSM and W-CDMA architectures in a device) the complexity increases since the active RAT must decide which of a number of passive RATs should be given radio time. When adding a new RAT, the already existing RATs have to be updated to be aware of radio need particulars associated with the new RAT. If the active RAT and the passive RAT are not well aligned radio usage conflicts can occur. Detection of radio access conflicts requires specific hardware design to address the issue, e.g., potentially extensive signaling between the RAT modules related to radio access time handling which can become very complicated as the number of RATs increases. Many interrupt signals and other signals are required, which makes current solutions inefficient and prone to errors. Existing solutions for adding additional RAT capabilities to a UE are also power inefficient, e.g., due to the excessive signaling and the requirement for knowledge in each RAT module of all other RATs in the device.
Accordingly, it would be desirable to provide methods and systems which reduce or remove the above described drawbacks associated with multi-RAT devices.